3-Benzisothiazolylpiperazine Derivatives as ... - ACS Publications

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Harry R. Howard,* John A. Lowe, III,* Thomas F. Seeger, Patricia A. Seymour, ... Patrick R. Maloney, Frank E. Ewing, Michael E. Newman, Anne W. Schmidt, ...

J. Med. Chem. 1996, 39, 143-148

143

3-Benzisothiazolylpiperazine Derivatives as Potential Atypical Antipsychotic Agents Harry R. Howard,* John A. Lowe, III,* Thomas F. Seeger, Patricia A. Seymour, Stevin H. Zorn, Patrick R. Maloney, Frank E. Ewing, Michael E. Newman, Anne W. Schmidt, Jerome S. Furman, Gwendolyn L. Robinson, Elisa Jackson, Celeste Johnson, and Jean Morrone Central Research Division, Pfizer Inc., Eastern Point Road, Groton, Connecticut 06340 Received August 22, 1995X

A series of substituted phenethyl derivatives of 3-benzisothiazolylpiperazine incorporating potent D2 and 5-HT2A antagonist activity was investigated as an approach to a novel atypical antipsychotic agent. The in vitro profile of 8e from this series is a combination of D2 receptor affinity comparable to the typical antipsychotic agent haloperidol and a 5-HT2A/D2 ratio comparable to the atypical agent clozapine. In vivo 8e possesses activity consistent with an efficacious antipsychotic agent with less tendency to induce extrapyramidal side effects in man. The atypical antipsychotic agents, exemplified by clozapine, 1, offer improved treatment of schizophrenia by combining efficacy with less propensity to cause harmful central nervous system (CNS) side effects.1 Recent attention in this field has been focused on determining which of clozapine's many in vitro attributes is responsible for its atypical profile. One hypothesis is based on the observation that clozapine, in common with other atypical antipsychotics, possesses a higher antagonist affinity at the serotonin 5-HT2A as compared with the dopamine D2 receptor.2 Risperidone, 2, which also has a favorable 5-HT2A/D2 ratio,3 has demonstrated clinical efficacy with a reduced propensity to induce extrapyramidal side effects (EPS),4 supporting the importance of this ratio. Two other extensively studied agents based on the clozapine structure, olanzapine, 3,5 and tiospirone, 4,6 are also reported to have favorable 5-HT2A/D2 ratios. (The ratio of affinities for the 5-HT2A and D2 receptors is reported as 5-HT2A/D2, calculated as (1/Ki value for the 5-HT2A binding)/(1/Ki value for the D2 binding).) Previous publications from this laboratory have described the design and synthesis of a series of potential atypical antipsychotic agents based on the structure of 1-naphthylpiperazine.7 In seeking to improve the dopaminergic antagonist potency of these compounds, and hence their potential clinical efficacy, we were attracted to the structure and biochemical profile of 4. The heteroatom-substituted phenethyl groups used in the 1-naphthylpiperazine series proved especially effective in maintaining a favorable 5-HT2A/D2 ratio and were expected to afford similarly promising properties when appended to the 3-benzisothiazolylpiperazine nucleus of 4. The following report chronicles the implementation of this strategy, which led to the discovery of the putative atypical antipsychotic agent 8e. Chemistry The preparation of the benzisothiazolylpiperazine derivatives is outlined in Scheme 1 and is based on our earlier work in the 1-naphthylpiperazine series.7 The synthesis of the oxindoles 5d,e began with WolffKishner reduction of the corresponding isatin. After Friedel-Crafts acylation with the appropriate chloroX

Abstract published in Advance ACS Abstracts, November 15, 1995.

0022-2623/96/1839-0143$12.00/0

Figure 1. Selected ‘atypical’ and putative ‘atypical’ antipsychotic agents.

acetyl chloride followed by triethylsilane/trifluoroacetic acid reduction of the resulting aryl ketone, the side chain 7 was appended to 3-benzisothiazolylpiperazine via base-catalyzed condensation in methyl isobutyl ketone (MIBK) or DMF. A troublesome side reaction, aldol condensation of the oxindole side chain with MIBK, led to a reduced yield of product in compounds 8d-8f. Physical properties of final products are listed in Table 3. Biology Compounds were tested for affinity at D2 and 5-HT2A receptors by homogenate binding in rat brain. Competitive inhibition of [3H]spiperone (D2) in rat striatum © 1996 American Chemical Society

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Journal of Medicinal Chemistry, 1996, Vol. 39, No. 1

Howard et al.

Scheme 1. Synthesis of 3-Benzisothiazolylpiperazine Derivatives

and [3H]ketanserin (5-HT2A) in frontal cortex was quantified and used to generate a pKi value for each compound of interest. Inhibition of serotonin-induced phosphatidylinositol turnover in rat brain cerebral cortical slices was used as a functional measure of 5-HT2 receptor antagonism. A standard rat brain homogenate binding assay was used to measure affinity for R1 noradrenergic receptors using [3H]prazosin. In vivo measurement of potential antipsychotic efficacy was determined by use of inhibition of d-amphetamineinduced hyperlocomotion in rats and inhibition of apomorphine-induced stereotypy in rats, both of which arise by stimulation of dopaminergic mechanisms. Another behavioral test associated with antipsychotic efficacy, the conditioned avoidance paradigm, measures the response of rats trained to avoid footshock signaled by an auditory cue. Antipsychotic agents have been shown to disrupt conditioned avoidance responding without impairment of escape responding. The tendency to induce catalepsy in rats was used as an indication of the propensity to cause EPS. Results and Discussion The first antipsychotic agent to qualify for the category of ‘atypical’, that is, an agent showing efficacy without causing EPS in patients, was clozapine (Figure 1). Given the unfortunate incidence of agranulocytosis with clozapine, there has been considerable effort to reproduce its clinical profile in a novel structure. Figure 1 outlines some of the agents resulting from these studies, which utilize a variety of strategies in an attempt to reach this goal. Our strategy was based on our previous observation,8 as well as on related studies,9 that the putative atypical antipsychotic agents possess greater affinity for the 5-HT2A receptor than the D2 receptor. A 92% correlation between an atypical profile and a 5-HT2A/D2 ratio of g3.2 or greater has also been demonstrated.10 In addition, the potent 5-HT2 receptor antagonist ritanserin has been reported to reduce the incidence of EPS produced by neuroleptic treatment11 and improve negative symptoms in schizophrenia.12 Thus a favorable 5-HT2A/D2 ratio was selected for optimization in vitro. Two ratios were selected for in vivo optimization. The first, catalepsy induction compared with blockade of amphetamine-induced hypermotility, was used to confirm the atypical profile pre-

dicted in vitro. The second ratio, blockade of spontaneous as compared with amphetamine-induced hypermotility, predicts relative sedative liability. The chemical strategy designed to afford the desired 5-HT2A/D2 ratio was based on our previously reported work using heterocyclic surrogates to mimic the catechol and indole portions of dopamine and serotonin, respectively.7 These oxindole-related heterocyclic groups, when appended to an arylpiperazine such as 1-naphthylpiperazine, afford high-affinity antagonists at both D2 and 5-HT2A receptors. In order to improve their D2 receptor affinity, these groups were appended to 3-benzisothiazolylpiperazine, a derivative of which, the putative atypical antipsychotic agent tiospirone, 4, was previously shown to possess potent D2 receptor affinity.6 Thus compounds 8a-c were found to possess both high D2 receptor affinity and selectivity for the 5-HT2A receptor, as shown in Table 1. Compound 8b seemed especially attractive for further modification due to its superior D2 receptor affinity. This greater affinity translates to better activity in vivo in blocking amphetamine-induced locomotor behavior in the rat, thought to be mediated by the mesolimbic dopamine system and thus predictive of antipsychotic efficacy, as shown in Table 2. In addition, the 5-HT2A/D2 ratio of 8b (Table 1) surpasses that of clozapine, risperidone, and tiospirone. The D2/R1 ratio of 8b, when compared with that of clozapine, suggests 8b might have a lower propensity to cause orthostatic hypotension, an effect generally thought to involve R adrenergic blockade. The superior 5-HT2A/D2 ratio of 8b is confirmed by its favorable ratio for blockade of amphetamine-induced locomotor activity, an efficacy model, compared with its induction of catalepsy, thought to be an indicator of the potential to induce EPS. As shown in Table 1, further modifications of 8b afforded compounds with similar affinity for the D2 receptor, with compounds 8d,e,g maintaining 8b’s favorable 5-HT2A/D2 ratio. To demonstrate 5-HT2A receptor antagonism, blockade of 5-HT stimulation of phosphatidylinositol turnover in rat brain cerebral cortical slices was employed.13 In this system 8e is a potent antagonist of the 5-HT-mediated response (Ki ) 2.3 ( 0.9 nM, Figure 2). It showed the best ratio of D2 to R1 receptor blockade and preserved the favorable in vivo ratio of amphetamine-induced to spontaneous hy-

Benzisothiazolylpiperazines as Antipsychotic Agents

Journal of Medicinal Chemistry, 1996, Vol. 39, No. 1 145

Table 1. In Vitro Characterization of 3-Benzisothiazolylpiperazine Derivatives

pKi values

Ki values

compd

X

Y

Z

D2

5-HT2A

Rc

8a 8b 8c 8d 8e 8f 8g 8h haloperidol clozapine risperidone tiospirone

NH NH NH NH NH NEt NH NH

O CH2 S CH2 CH2 CH2 C(CH3)2 C(CH2)4

H H H F Cl H H H

8.20 ( 0.03 (4) 8.42 ( 0.03 (5) 8.29 ( 0.11 (3) 8.38 ( 0.06 (3) 8.32 ( 0.04 (6) 8.53 ( 0.08 (3) 8.51 ( 0.11 (3) 8.38 ( 0.07 (3) 9.15 ( 0.04 (3) 7.08 ( 0.08 (6) 8.43 ( 0.03 (4) 8.67 ( 0.08 (6)

9.81 ( 0.06 (4) 9.52 ( 0.07 (6) 9.57 ( 0.08 (3) 9.45 ( 0.05 (3) 9.38 ( 0.04 (5) 8.84 ( 0.08 (3) 9.48 ( 0.05 (3) 8.84 ( 0.05 (3) 7.35 ( 0.13 (5) 7.82 ( 0.05 (3) 9.27 ( 0.04 (4) 9.24 ( 0.03 (6)

8.38 ( 0.06 (4) 8.52 ( 0.07 (3) 8.63 ( 0.11 (3) 8.19 ( 0.12 (5) 7.98 ( 0.04 (3) 8.35 ( 0.13 (5) 8.68 ( 0.14 (4) 8.29 ( 0.06 (3) 8.20 ( 0.11 (4) 8.25 ( 0.11 (4) 9.13 ( 0.15 (3) 8.83 ( 0.13 (4)

a

b

a

D2

6.3 3.8 5.1 4.2 4.8 3.0 3.1 4.2 0.71 83 3.7 2.1

affinity ratios

5-HT2A

Rc

D2/5-HT2A

D2/R

0.15 0.30 0.27 0.35 0.42 1.4 0.33 1.4 45 15 0.54 0.58

4.2 3.0 2.3 6.5 11 4.5 2.1 5.1 6.3 5.6 0.74 1.5

42 13 19 12 11 2.1 9.4 3.0 0.016 5.5 6.8 3.6

1.5 1.3 2.2 0.65 0.44 0.67 1.5 0.82 0.11 15 5.0 1.4

b

a Binding to the D dopamine receptor in rat brain, using [3H]NPA as ligand, given as the pK value followed by SEM and number of 2 i determinations in parentheses, with the Ki value in the adjacent column in nM units for comparison and generation of ratios. pKi values were determined from dose-response curves of three log concentrations of the test compounds, each concentration in triplicate. b Binding to the 5-HT2 serotonin receptor in rat brain, using [3H]ketanserin as ligand, given as the pKi value followed by SEM and number of determinations in parentheses, with the Ki value in the adjacent column in nM units for comparison and generation of ratios. pKi values were determined from dose-response curves of three log concentrations of the test compounds, each concentration in triplicate. c Binding to the R adrenergic receptor in rat brain, using [3H]prazosin as ligand, given as the pKi value followed by SEM and number of determinations in parentheses, with the Ki value in the adjacent column in nM units for comparison and generation of ratios. pKi values were determined from dose-response curves of three log concentrations of the test compounds, each concentration in triplicate.

Table 2. In Vivo Characterization of 3-Benzisothiazolylpiperazine Derivatives ED50 (po) values, mg/kg compd 8a 8b 8c 8d 8e 8f 8g 8h haloperidol clozapine risperidone tiospirone

ratios

ampha

sponb

apomc

4.2 (2.7-5.9) 1.4 (0.35-3.6) 2.7 (2.3-3.2) 1.0 (0.65-1.4) 1.5 (1.1-2.5) 1.1 (N ) 1) 2.3 (1.1-3.6) 5.8 (1.2-16.8) 0.14 (0.10-0.20) 12.8 (7.1-25.7) 0.44 (0.23-0.72) 4.8 (N ) 1)

9.8 (7.0-14.6) 8.5 (3.7-12.6) 2.7 (1.1-5.5) 3.1 (1.8-5.1) 8.9 (5.3-19.1) 2.1 (0.95-3.2) 10.7 (7.6-20.5) NT

21.6 (6.3-74) 8.4 (5.7-12.3) 23.8

18.8 (15.1-23.4) >56

9.1

17.8

2.4 (1.5-3.9) 4.7

12.1 (9.7-15.1) 10

10

17.8

2.6 (0.42-5.0) 1.8 (0.13-4.13) 2.6

9.0

32

NT

0.25 (0.19-0.33) >32.0

0.79 (0.43-1.5) >32.0

0.93 (0.49-1.7) >17.8

1.8 (1.2-2.9) 18.8 (6.6-54)

5.7 (3.7-8.8) 20.1 (7.8-51.9)

1.6 (0.57-4.4) 11.7 (5.0-27)

0.68 (0.27-1.4) 8.18 (4.7-18.3) 1.2 (0.85-1.74) 15.5 (11.1-24.0)

catad >32

conde

spon/amph

cata/amph

17.8

2.3

7.6

6.7 (5.1-8.7) 12.3 (6.9-22) 9.0

6.1

21

1.0

>20

3.1

16

5.9

8.1

1.9

6.2

4.7

8.1 4.8

4.9 0.64 2.7 3.2

5.6 >32 13 6.7

a Inhibition of amphetamine-induced locomotor behavior in rats, via oral administration. The 95% confidence limits are given in parentheses beneath, except for those compounds tested once, as indicated. b Inhibition of spontaneous locomotor behavior in rats, via oral administration. The 95% confidence limits are given in parentheses beneath, except for those compounds tested once, as indicated. c Inhibition of apomorphine-induced stereotypy in rats, via oral administration. The 95% confidence limits are given in parentheses beneath, except for those compounds tested once, as indicated. For these latter compounds, the value indicated is an MED50 value. d Induction of catalepsy in rats, via oral administration. The 95% confidence limits are given in parentheses beneath, except for those compounds tested once, as indicated. e Inhibition of conditioned avoidance response in rats, via oral administration. The 95% confidence limits are given in parentheses beneath, except for those compounds tested once, as indicated.

permotility blockade found in 8b. Compound 8e also blocked conditioned avoidance responding in rats without impairing escape responding, indicative of efficacy with minimum liability to produce sedative side effects. On the basis of these results, 8e, ziprasidone, has been selected for further evaluation in clinical trials in man.

Conclusion The series of 3-benzisothiazolylpiperazine derivatives described in this report provides support for the hypothesis that a favorable ratio of 5-HT2A/D2 receptor binding affinity translates to less induction of catalepsy as compared with blockade of amphetamine-induced

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Figure 2. Effect of 8e on 5-HT2 receptor-stimulated phosphatidylinositol turnover in rat brain cerebral cortical slices. Each point is the mean inhibition of the 5-HT (100 mM)induced effect and represents the mean of 3-5 data points ( SEM derived from separate experiments each performed in triplicate. Table 3. Physical Properties of 3-Benzisothiazolylpiperazine Derivatives compd

yield, %

mp, °C

formula

8a 8b 8c 8d 8e 8f 8g 8h

50 59 77 19 20 25 40 50

185-187 288-288.5 288-290 291-293 >300 278-279 289-291 291-293 dec

C20H20N4O2S‚0.5H2O C21H22N4OS‚1.25HCl C20H20N4OS2‚HCl‚H2O C21H21FN4OS‚HCl‚H2O C21H21CIN4OH‚HCl‚0.5H2O C23H26N4OS‚HCl‚CH2Cl2 C23H26N4OS‚HCl‚0.5H2O C25H28N4OS‚HCl‚0.5H2O

locomotor activity. In particular, compound 8e optimizes these properties and has modest R1 receptor affinity and a minimal tendency to block spontaneous locomotor activity, indicating a reduced propensity to cause hypotension and sedation in the clinic, respectively. The in vitro profile of 8e is thus a combination of D2 receptor affinity comparable to the typical antipsychotic agent haloperidol and a 5-HT2A/D2 ratio comparable to the atypical agent clozapine. The ultimate confirmation of the hypothesis that this in vitro profile combined with its favorable in vivo activity will result in an effective antipsychotic with low EPS liability awaits the outcome of clinical evaluation of 8e. Experimental Section Melting points were obtained on a Hoover melting point apparatus and are uncorrected. NMR spectra were obtained on a Varian XL-300 or Bruker AM-300 spectrometer, with tetramethylsilane as internal standard. IR spectra were obtained on Perkin-Elmer 283B and 1420 spectrometers. Mass spectra were obtained on a Finnegan 4510 mass spectrometer, and high-resolution mass spectra were obtained on an AE-9 instrument. TLC analysis was carried out on EM Kieselgel 60 F254 5 × 20 cm plates. Elemental analyses were carried out by the Analytical Laboratory of Pfizer Central Research and are within (0.4% of theory unless otherwise noted. Radioisotopic ligands were purchased from New England Nuclear, Boston, MA, or Amersham, Arlington Heights, IL. Apomorphine hydrochloride and d-amphetamine were purchased from Research Biochemicals Inc. (Natick, MA). Risperidone was a gift of Janssen, Inc., tiospirone was a gift of Bristol-Myers Squibb, Inc., and clozapine was a gift of Sandoz, Inc. Other reagents were obtained from Sigma Chemical Co. (St. Louis, MO). Syntheses. The examples presented below illustrate the method for preparation of the compounds listed in Table 3;

Howard et al. physical data for the compounds are listed there. The following compounds were prepared by literature methods: 3-benzisothiazolylpiperazine,6 6a-c,7 7a-c,7 5d,14 5e,14 and 5g.15 Compounds 5d-h were converted to 7d-h by the method used for 7a-c.7 General Method for the Preparation of 4-Substituted (1,2-Benzisothiazol-3-yl)piperazines 8. 6-(2-(4-(1,2-Benzisothiazol-3-yl)piperazinyl)ethyl)benzoxazolone (8a). To a solution of 1.22 g (5.02 mmol) of 6-(2-bromoethyl)benzoxazolone and 1.10 g (5.02 mmol) of 3-(1,2-benzisothiazolyl)piperazine in 40 mL MIBK were added 0.53 g (5.02 mmol) of sodium carbonate and 2 mg of sodium iodide. The mixture was refluxed for 3 days, cooled, and evaporated. The residue was taken up in ethyl acetate and chromatographed on silica gel using ethyl acetate as eluent. The product fractions were concentrated and triturated with isopropyl ether to afford a white solid, mp 183-186 °C, 962 mg (50%). Rf ) 0.2 in ethyl acetate. 1H-NMR (δ, DMSO-d6): 2.6-2.9 (m, 8H), 3.5 (m, 4H), 7.05 (m, 2H), 7.23 (s, 1H), 7.46 (t, 1H), 7.57 (t, 1H), 8.07 (d, 2H), 11.5 (bs, 1H). IR (cm-1, KBr): 1762 (CdO). MS (m/e, %): 380 (parent, 1), 232 (22), 93 (21), 81 (20), 80 (26), 78 (100), 65 (39), 63 (67), 61 (47). Anal. (C20H20N4O2S‚1/2 H2O) C, H, N. 5-(2-(4-(1,2-Benzisothiazol-3-yl)piperazinyl)ethyl)-1,3dihydro-2(1H)-indol-2-one (8b): prepared in 59% yield as the hydrochloride salt, mp 288-288.5 °C. 1H-NMR (δ, DMSOd6): 3.1 (m, 2H), 3.4 (m, 4H), 3.51 (s, 2H), 3.5-3.8 (m, 4H), 4.1 (m, 2H), 6.81 (d, 1H), 7.1-7.2 (m, 2H), 7.49 (t, 1H), 7.62 (t, 1H), 8.14 (t, 2H). 13C-NMR (δ, DMSO-d6): 176.3, 162.2, 152.2, 142.5, 129.6, 128.2, 127.7, 127.0, 126.3, 124.9, 124.7, 124.1, 121.3, 19.2, 56.6, 50.5, 46.6, 35.8, 29.0. IR (cm-1, KBr): 1697 (CdO). MS (m/e, %): 378 (parent, 1), 233 (14), 232 (100), 177 (16), 91 (11), 56 (11). Anal. (C21H22N4OS‚1.25HCl) C, H, N. 6-(4-(2-(1,2-Benzisothiazol-3-yl)piperazinyl)ethyl)benzothiazolone (8c): prepared in 77% yield as the hydrochloride hydrate, mp 288-290 °C. 1H-NMR (δ, DMSO-d6): 3.13.7 (m, 10H), 4.1 (m, 2H), 7.0-8.1 (m, 7H). IR (cm-1, KBr): 1680 (CdO). MS (m/e, %): 396 (parent, 1), 233 (16), 232 (100), 177 (19), 98 (4), 97 (4), 56 (7). Anal. (C20H20N4OS2‚HCl‚H2O) C, H, N. 5-(2-(4-(1,2-Benzisothiazol-3-yl)piperazinyl)ethyl)-6fluoro-1,3-dihydro-2(1H)-indol-2-one (8d): prepared in 19% yield as the hydrochloride hydrate, mp 291-293 °C. 1HNMR (δ, CD3OD): 3.15 (m, 2H), 3.4-3.6 (m, 8H), 3.80 (m, 2H), 4.20 (d, 2H), 6.7 (d, 1H), 7.22 (d, 1H), 7.47 (t, 1H), 7.57 (t, 1H), 7.95 (d, 1H), 8.05 (d, 1H). MS (m/e, %): 396 (M+, 1), 232 (100), 177 (53), 91. Anal. (C21H21FN4OS‚HCl‚H2O) C, H, N. 5-(2-(4-(1,2-Benzisothiazol-3-yl)piperazinyl)ethyl)-6chloro-1,3-dihydro-2(1H)-indol-2-one (8e): prepared in 20% yield using isoamyl alcohol instead of MIBK as the hydrochloride hemihydrate, mp >300 °C. 1H-NMR (δ, DMSO-d6): 3.153.60 (m, 10H), 3.72 (d, 2H), 4.10 (d, 2H), 6.88 (s, 1H), 7.28 (s, 1H), 7.48 (t, 1H), 7.60 (t, 1H), 8.14 (dd, 2H), 10.6 (s, 1H), 11.4 (bs, 1H). MS (m/e, %): 412 (M+, 0.4), 233 (18), 232 (100), 177 (19). IR (KBr, cm-1) 1708, 1628, 1489. Anal. (C21H21ClN4OS‚HCl‚1/2H2O) C, H, N. 5-(2-(4-(1,2-Benzisothiazol-3-yl)piperazinyl)ethyl)-1ethyl-1,3-dihydro-2(1H)-indol-2-one (8f): prepared in 25% yield as the hydrochloride salt, mp 278-279 °C. 1H-NMR (δ, CD3OD): 1.25 (t, 3H), 3.18 (m, 2H), 3.50 (m, 8H), 3.75 (m, 4H), 4.20 (d, 2H), 5.24 (s, 2H, CH2Cl2 - one mole), 7.0 (d, 1H), 7.30 (s+d, 2H), 7.48 (t, 1H), 7.55 (t, 1H), 7.98 (d, 1H), 8.08 (d, 1H). MS (m/e, %): 406 (M+, 1), 232 (100), 177, 163. Anal. (C23H26N4OS‚HCl‚CH2Cl2) C, H, N. 5-(2-(4-(1,2-Benzisothiazol-3-yl)piperazinyl)ethyl)-3,3dimethyl-1,3-dihydro-2(1H)-indol-2-one (8g): prepared in 40% yield as the hydrochloride hemihydrate, mp 289-291 °C. 1H-NMR (δ, CD OD): 1.35 (s, 6H), 3.10 (m, 2H), 3.4-3.6 (m, 3 10H), 6.92 (d, 1H), 7.15 (d, 1H), 7.22 (s, 1H), 7.45 (t, 1H), 7.55 (t, 1H), 7.95 (d, 1H), 8.05 (d, 1H). MS (m/e, %): 406 (M+, 1), 324, 232 (100), 177, 146. Anal. (C23H26N4OS‚HCl‚1/2H2O) C, H, N. 5′-(2-(4-(1,2-Benzoisothiazol-3-yl)piperazinyl)ethyl)3,3-spirocyclopentane-1,3-dihydro-2(1H)-indol-2-one (8h): prepared in 50% yield as the hydrochloride hemihydrate, mp 291-293 °C. 1H-NMR (δ, CDCl3): 1.6-2.1 (m, 8H), 3.0-

Benzisothiazolylpiperazines as Antipsychotic Agents 3.25 (bs + m, 6H), 3.45 (d, 2H), 4.0 (d, 4H), 6.70 (d, 1H), 6.92 (d + s, 2H), 7.25 (t, 1H), 7.40 (t, 1H), 7.75 (dd, 2H), 9.3 (s, 1H). MS (m/e, %): 432 (M+,

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